1. Field of the Invention
The present invention relates to electronic systems, and in particular to a system and method for managing thermal power dissipation utilizing a thermally conducting plate such as, but not limited to a vapor plate that is thermally and mechanically connected to a microprocessor and a power regulator module.
2. Description of the Related Art
Vapor plates are extremely efficient configurations for providing thermal power dissipation in small form factors. Vapor plates have been used for many years in a variety of applications to remove thermal power from heat generating entities including electronic circuits. The vapor plate relies on vaporization and condensation of a liquid in a closed system eliminating the need for an external reservoir or flowing liquid. Also, because the temperature difference between the vaporization zone of the vapor plate and the condensation zone is usually very small, (several degrees centigrade) thermal conductivity can be as much as two orders of magnitude greater than phonon conduction through condensed media such as solid copper plates.
Although vapor plates are highly desirable from the standpoint of thermal power dissipation for microelectronic applications requiring form factor minimization, the comparative cost between the vapor plate and conventional, finned heatsinks with solid metallic bases is often prohibitive. Also, for systems requiring multiple thermal power dissipation paths, the vapor plate must often be dedicated to thermal power dissipation from only one component such as a microprocessor.
In high-performance desktop or high-end workstation/servers, high-speed microprocessor packaging must be designed to provide increasingly small form-factors. Meeting end user performance requirements with minimal form-factors while increasing reliability and manufacturability presents significant challenges in the areas of power distribution, thermal management, and electromagnetic interference (EMI) containment.
To increase reliability and reduce thermal dissipation requirements, newer generation processors are designed to operate with reduced voltage and higher current. Unfortunately, this creates a number of design problems.
First, the lowered operating voltage of the processor places greater demands on the power regulating circuitry and the conductive paths providing power to the processor. Typically, processors require supply voltage regulation to within 10% of nominal. In order to account for impedance variations in the path from the power supply to the processor itself, this places greater demands on the power regulating circuitry, which must then typically regulate power supply voltages to within 5% of nominal.
Lower operating voltages have also lead engineers away from centralized power supply designs to distributed power supply architectures in which power is bused where required at high voltages and low current, where it is converted to the low-voltage, high-current power required by the processor from nearby power conditioning circuitry.
While it is possible to place power conditioning circuitry on the processor package itself, this design is difficult to implement because of the unmanageable physical size of the components in the power conditioning circuitry (e.g. capacitors and inductors), and because the addition of such components can have a deleterious effect on processor reliability. Such designs also place additional demands on the assembly and testing of the processor packages as well.
Further exacerbating the problem are the transient currents that result from varying demands on the processor itself. Processor computing demands vary widely over time, and higher clock speeds and power conservation techniques such as clock gating and sleep mode operation give rise to transient currents in the power supply. Such power fluctuations can require changes of hundreds of amps within a few nanoseconds. The resulting current surge between the processor and the power regulation circuitry can create unacceptable spikes in the power supply voltage (e.g.                     ⅆ        v            =              IR        +                  L          ⁢                                    ⅆ              i                                      ⅆ              t                                            )    .
Thermal management must also take nearby voltage regulator efficiencies into account. An 85% efficient voltage regulator driving a 130 watt device dissipates over 20 watts. This makes it more difficult to locate the voltage regulator close to the processor because the thermal management structures for each component conflict. The need for higher performance and increased functional integration in smaller processor dies has also lead to higher heat-flux concentrations in certain areas of the processor die. In some cases, the resulting surface energy densities approach unmanageable levels. Processor reliability is exponentially dependent on the operating temperature of the die junction. Lowering temperatures in the order of 10-15 degrees centigrade can double the processor lifespan. Thermal management issues now present some of the largest obstacles to increases in processor speed and miniaturization of the processor package.
To address the requirements described above, the present invention discloses a stack up assembly. The stack up assembly comprises a VRM circuit board or power regulation module, having a first side and a second side; a thermally conductive plate such as a vapor plate having a first side and a second side, wherein the thermally conductive plate first side is thermally coupled to the second side of the VRM circuit board; and a microprocessor having a first side and a second side, the microprocessor first side thermally coupled to the vapor plate second side.
The power regulator module, vapor chamber and microprocessor are configured in a three dimensional architecture that utilizes and extends the capability of a low cost, coaxial interconnection with power standoffs and modifications thereof, by physically integrating the high current delivery capability of the power standoffs into custom designed power regulators to provide self-contained and physically separable power delivery modules.
The three dimensional architecture of this invention thermally and mechanically connects the thermally conducting plate to both the microprocessor and the power regulator using thermal interface materials. Also, the three dimensional architecture configures a custom designed, electrically conductive frame and associated fittings and hardware that encases the microprocessor, power delivery module and other circuits to minimize and contain EMI within the package rather than within the chassis in a configuration that minimizes the overall form factor.